This invention generally concerns electric heating arrangements. More specifically, the present invention relates to an electric heating arrangement for spray nozzles, such as those used to spray plastics, in which a highly compressed tubular heating body, provided with a metal jacket, is arranged in coil form directly on the nozzle body.
Conventional electrically heated spray nozzles, or injection jets for plastics or synthetics, include, for example, the nozzle disclosed in Ger. Pat. No. 3,100,092. To obtain the necessary good transfer of heat from the heating element to the nozzle, the tubular heating body coil is imbedded, in this case, in a highly compressed metal powder, and this structure is surrounded by a sheathing tube. This construction requires a certain extra expense and the total diameter of the spray nozzle becomes greater thereby, which is not always desirable.
A conventional heating arrangement of a similar kind is shown in Ger. Pat. No. 2,250,778. Here, the object to be heated is provided with a spiral groove which receives a heating cable. This construction also is surrounded by a covering sheath. Extra expense and an increased total diameter are to be noted here also.
Accordingly, it has been considered desirable to develop a new and improved electric heating arrangement for a spray nozzle which would overcome the foregoing difficulties and others while providing better and more advantageous overall results.